AirHint found the following cheapest return flights from Chiang Mai (CNX) to London (LGW) in September 2025 (see full year).

Return flights

27 Sep - 13 Oct	AirAsia
05 Sep - 19 Sep	Thai AirAsia
04 Sep - 11 Sep	China Eastern
03 Sep - 16 Sep	China Eastern
02 Sep - 05 Oct	Thai AirAsia
04 Sep - 14 Sep	Air China
29 Sep - 21 Oct	Singapore Airlines
29 Sep - 29 Oct	Singapore Airlines
22 Sep - 29 Sep	Singapore Airlines

Also check the deals for one-way flights from Chiang Mai to London in September.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Chiang Mai to London in September from 629€

Return flights